1. Field of the Invention
The present invention relates to an image forming system, and more particularly to an image forming system comprising an image forming apparatus and a post-processing apparatus having a function as a sorter, a stapler or the like.
2. Description of Related Art
Image forming apparatuses are generally structured to print images on papers of regular sizes, such as A4, A3, etc. However, there are cases in which printing on longer papers is required.
Conventionally, image forming apparatuses provided with post-processing apparatuses having functions as sorters, staplers or the like have a problem that a paper jam is likely to occur when a long paper is fed therein, and therefore such image forming apparatuses are constructed not to perform printing on long papers. This prevents users who desire printing on long papers from attaching post-processing apparatuses to their image forming apparatuses.
On contrary, when printing on long papers is to be performed by use of an image forming apparatus provided with a post-processing apparatus, the user has to take measures, for example, request an engineer having special knowledge and skill to detach the post-processing apparatus from the image forming apparatus. Thus, conventional image forming systems have been far away from meeting both of the demands for various functions by use of a post-processing apparatus and for printing on long papers by use of an image forming apparatus.
In order to comply with the demand for printing on long papers, some types of image forming apparatuses have been introduced into the market. Also, Japanese Patent Laid-Open Publication Nos. 2003-98765, 2003-81494, 2002-348051 and 10-316298 have raised suggestions about printing and/or post-processing on long papers.
However, in order to enable printing on long papers in an image forming apparatus provided with a post-processing apparatus, the post-processing apparatus shall be complicatedly structured, and in view of cost and skill, it is almost impossible to actually construct the post-processing apparatus. The prior arts premise that long papers are to be aligned, stapled, punched, folded and/or sorted, and the structure for the purpose is complicate. Further, combining the complicate structure with a mechanism for feeding the long papers is technically more difficult, and in view of cost and size, it is practically impossible.
For example, a task for feeding a long paper to a post-processing apparatus is providing a secure guide to prevent askew feeding of papers. The post-processing apparatus incorporates, for example, a mechanism for stapling papers, and further providing the post-processing apparatus with a large-size guide for preventing stacking of askew-fed long papers results in an increase in size and an increase in cost.